The present invention relates to improved systems and methods for controlling a write-once memory to prevent inadvertent writing or erasing.
Non-volatile memory is becoming standard in many products such as digital cameras and digital audio players. Traditional non-volatile memory has been rewritable, allowing the data storage system to erase and write over existing data.
With the advent of more cost-effective write-once memory devices, a mechanism is needed to prevent existing data storage systems from performing destructive operations (such as erase or write) to the write-once memory device.
The embodiments described below include a memory device having a write-once memory array, an electronically resetable flag, and a memory array controller. The controller prevents writing into and erasing from the write-once memory device unless the flag is in a selected state.
This memory device is used with a data storage system that automatically determines whether a memory device installed in the data storage system is a write-once memory device, and automatically sends a recognition signal to the memory device when the installed memory device is determined to be a write-once memory. The memory device responds to the recognition signal by setting the flag to the selected state, and the memory device controller automatically refuses to implement write and erase commands prior to receipt of the recognition signal, while implementing such destructive commands subsequent to the receipt of the recognition signal. At all times, regardless of the state of the flag, the memory array controller implements nondestructive commands such as status and read commands.
Because the memory device does not implement destructive commands until the recognition signal is received, data storage systems that are not suited to use with write-once memories are prevented from altering the contents of the write-once memory array.
This section has been provided by way of general introduction, and it is not intended to limit the scope of the following claims.